Technical Field
The present invention relates to methods and compositions for removal of methyl tertiary butyl ether (MTBE) from contaminated water sources and systems. More particularly, the present invention relates to metal modified carbon fly ash and methods of treating MTBE-contaminated water sources and systems with the modified carbon fly ash.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Methyl tertiary butyl ether (MTBE) is an established contaminant of water sources, following its large scale utilization as gasoline oxygenate, in replacement of tetra-ethyl lead (Rick C., Barbara R., John Z., (2001). National Survey of MTBE and other VOCs in Community Drinking-Water Sources, U.S. Geological Survey, FS-064-01—incorporated herein by reference in its entirety. Leakage from underground storage tanks, spills during production, transportation and at gasoline filling stations account for the major sources of environmental contamination. The high solubility of about 50,000 mg/L, low organic-carbon partition coefficient Koc (11 mg/L) and poor natural degradation make it persistent in the environment, as it migrates easily in the water system, with little tendency of being confined to the origin of contamination (Squillace P. J., Pope D. A., Price C. V., (1995). Occurrence of the gasoline additive MTBE in shallow ground water in urban and agricultural areas (U.S. Geological Survey Fact Sheet FS-114-95, p. 4—incorporated herein by reference in its entirety) coupled with the unpleasant odor and taste introduced into the contaminated system are the primary concerns associated with MTBE. However, the US Environmental Protection Agency considers MTBE to be a potential human carcinogen, with advisory level for MTBE ranging from 20 to 40 μg/L (U.S. Environmental Protection Agency, (1997b). Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Methyl Tertiary-Butyl Ether (MTBE). Washington, D.C.: U.S. Environmental Protection Agency, Office of Water, EPA-822-F-97-009—incorporated herein by reference in its entirety).
Remediation technologies such as adsorption with activated carbon or charcoal filters, air stripping, and ultraviolet/hydrogen peroxide (Fenton) treatment have recorded varying levels of success with MTBE. However, each technique is characterized by its inherent limitations, which creates the continuous need for improvements in the removal of MTBE from contaminated water sources. Adsorption based treatments of MTBE contaminated systems face a major challenge from the high solubility and low organic-carbon properties of MTBE. However, granular activated carbon has recorded significant success in removal of MTBE from aqueous solution, hence regarded as the established adsorbent of MTBE (Sutherland J., Adams C., Kekobad J., (2004). Treatment of MTBE by air stripping, carbon adsorption, and advanced oxidation: technical and economic comparison for five groundwaters, Water Research, 38(1), pp. 193-205—incorporated herein by reference in its entirety). Impregnation of adsorbent materials with selected metal oxides has been reported to improve their adsorption efficiencies, as several studies have shown for impregnated activated carbon and other low surface area materials like fly ash (Wan Ngah, W. S., and Hanafiah, M. A. K. M. (2008)). Removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: a review. (Bioresource technology, 99(10), 3935-3948—incorporated herein by reference in its entirety). Scientific studies into the use of readily available low cost materials for the removal of environmental contaminants such as heavy metals and other organic pollutants have gained significant attention.
Fly ash (FA) constitutes the major particulate waste by-product during the generation of electricity by burning of coal or heavy liquid fuel. Fly ash is generated as a non-combustible, fine residue, carried in the flue gas and usually collected with the aid of electrostatic precipitators, and having a uniform size distribution of particles ranging 1 to 10 μm (Khairul N. I., Kamarudin H. and Mohd S. I. (2007). Physical, chemical & mineralogical properties of fly ash. Journal of Nuclear and Related Technology 4, 47-51—incorporated herein by reference in its entirety). Presently, the major applications of fly ash are in soil stabilization and as additives in the manufacturing of cements, with a large proportion of the fly ash material being disposed by land filling. The potential for utilizing fly ash as an inexpensive adsorbent was driven by its high alumina and silica content, where it could be adopted as liner for landfills to minimize leachate of organic pollutants (Mott H. V., Weber W. J. (1992). Journal of Environmental Science and Technology, 26, pp 1234—incorporated herein by reference in its entirety).
Application of fly ash as adsorbent of contaminant in aqueous solution is considered to be an alternative form of waste management, in place of the disposal in landfills. Raw fly ash and other modifications to it have been assessed for their removal efficiencies of several environmental contaminants in previous studies (Yadla, S. V., Sridevi, V., & Lakshmi, M. C. (2012). Adsorption performance of fly ash for the removal of lead. International Journal of Engineering Research & Technology, 1(7); Visa, M., & Duta, A. (2013). Methyl-orange and cadmium simultaneous removal using fly ash and photo-Fenton systems. Journal of hazardous materials, 244, 773-779; Ragheb, S. M. (2013). Phosphate removal from aqueous solution using slag and fly ash. HBRC Journal, 9(3), 270-275—each incorporated herein by reference in its entirety). However, their capacity for removal of MTBE from aqueous solution remains unsubstantiated.
In view of the foregoing, it will be advantageous to design methods and compositions that can efficiently treat MTBE contaminated water systems at a low economic cost. Disclosed embodiments of the present invention overcome the shortcomings of the prior art as described herein.